The invention pertains to the field of electronic circuit arrangements, by means of which wake-up and action signals are applied to microprocessors.
It is known that microprocessors are used for controlling various actuators. In particular, microprocessors are also used for control purposes in the automotive industry. These microprocessors must continue to operate when the engine is shut off. One example of such a control unit is a door control unit. In order to reduce the load on the car battery from control devices that contain such microprocessors, it was proposed to toggle the microprocessor between a quiescent mode and operating mode. This can be realized by utilizing a corresponding monitoring device: a so-called watchdog. It is quite obvious that much less current is consumed during the intervals that the microprocessor is in quiescent mode as opposed to operating mode. Due to the circuit design, unused cross currents that also load the battery in quiescent mode flow through the circuit arrangement connected in series on the input side of the microprocessor.
When the microprocessor is in operating mode, the corresponding inputs to which action signals may be applied are scanned by the microprocessor. If an action signal is not applied to any of these inputs, the microprocessor switches back to quiescent mode. Consequently, an action signal can only cause the microprocessor to execute the desired operation if the microprocessor is coincidentally in the operating mode. In order to prevent the occurrence of an unnecessarily long waiting period before the desired operation takes place following the generation of an action signal by the user, the toggle frequency between quiescent mode and operating mode of the microprocessor must be designed such that mode changes take place approximately every 80-100 ms. A delay greater than 100 ms may be noticeable to the user and perceived as an inconvenience. During the adjustment of such circuitry, the required transition time for the microprocessor clock must also be taken into consideration, with the transition time usually lying between 5 ms and 20 ms.
Although this toggling results in reduced current consumption in comparison to circuit arrangements that do not toggle between a quiescent mode and an operating mode, the microprocessor is frequently switched to operating mode when no control operation is to be performed.
Based on the previously discussed state of the art, the invention is based on the objective of making available an electronic circuit arrangement for applying wake-up and action signals to a microprocessor that makes it possible to achieve a further reduction in current consumption in comparison to the above-mentioned state of the art.
According to the invention, this objective is attained with an electronic circuit arrangement for applying wake-up and action signals to a microprocessor which contains at least one external switch that is assigned to the circuit arrangement and serves for generating said signals, where said circuit arrangement contains a quiescent mode circuit for generating a wake-up signal that triggers a wake-up interrupt when the microprocessor must be switched from quiescent mode into operating mode and an operating mode circuit for generating action signals, where the quiescent mode circuit is connected to a wake-up-compatible digital input of the microprocessor and the operating mode circuit is connected to an analog input of the microprocessor, where at least one said external switch is assigned to both circuits, where said circuit arrangement also contains switching means, whereby the circuit arrangement can be switched between operation of the quiescent mode circuit and operation of the operating mode circuit as a function of the operating mode of the microprocessor (quiescent mode or operating mode) when the other respective circuit is switched off, where the wake-up-compatible input of the microprocessor is configured by utilizing a predetermined threshold voltage or a threshold voltage interval in such a way that this input generates a wake-up interrupt when the wake-up signal corresponds to either a logical 0 or 1, where the logical 0 corresponds to a voltage below the threshold voltage and the logical 1 corresponds to a voltage above the threshold voltage.
Due to the circuit arrangement according to the invention, a wake-up interrupt is generated at the wake-up-compatible digital input of the microprocessor only if the microprocessor actually must take over or execute certain functions. Consequently, current is only consumed when it is required that the microprocessor be operational. In order to prevent undesirable cross currents from flowing during quiescent mode, the circuit arrangement contains a quiescent mode circuit and an operating mode circuit, where current is prevented from flowing in the operating mode circuit during quiescent mode due to the arrangement of a suitable switching means. Consequently, no cross current will flow. Conversely, the quiescent mode circuit is interrupted from operating mode.
In addition, in the present invention the wake-up-compatible input of the microprocessor can be configured in such a way that a wake-up interrupt is generated as a function of the chosen configuration, namely when the wake-up signal corresponds to one of a logical 0 or 1. For this purpose, the wake-up-compatible input of the microprocessor is preferably configured in such a way that predetermined threshold voltages separate the logic levels, where a logical 0 corresponds to a voltage below the lower threshold voltage and a logical 1 corresponds to a voltage above the upper threshold voltage. However, it would also be conceivable to define only one threshold voltage to separate a logical 0 from a logical 1 instead of the previously described threshold voltage interval with upper and lower threshold voltages. Consequently, a voltage that does not generate a wake-up interrupt is applied to the wake-up-compatible input in quiescent mode. Only when an action must be triggered or controlled by the microprocessor due to the actuation of the external switch does a corresponding voltage rise or a corresponding voltage drop, i.e., a trigger, occur depending on the configuration of the microprocessor input such that the desired wake-up interrupt is realized due to the changed voltage.
According to one particularly practical embodiment, it is proposed that the wake-up interrupt be generated when a logical 0 is applied to the wake-up-compatible microprocessor input, i.e., a wake-up interrupt is generated by a voltage drop at this input. Such a voltage drop can be realized e.g., by connecting a pull-up resistor, which is connected to a power supply regulator, to the quiescent mode circuit via a switching means. The voltage made available by the voltage regulator is correspondingly applied to the wake-up-compatible input of the microprocessor. The external switch is also connected to the wake-up-compatible input of the microprocessor via a control line. A resistor is inserted into this control line such that a voltage divider is formed in cooperation with the pull-up resistor and the control line that is connected to the wake-up-compatible input of the microprocessor. Once the switch is actuated, the quiescent mode circuit is closed such that the voltage divider is effectively engaged by the pull-up resistor and the resistor arranged it the control line, so that a voltage drop below the threshold voltage takes place at the microprocessor input. This triggers the wake-up interrupt of the microprocessor in the form of a logical 0.
Once the microprocessor clock is in steady state and is stable, the switching means assigned to the pull-up resistor is opened and the switching means provided for switching off the operating mode circuit is/are closed. The action signals generated as a result of the external switching means remaining closed or due to repeated or additional actuation of this switching means are applied to the analog input of the microprocessor which is now functional due to the available A/D converter.
A preferred circuit arrangement contains the components for operating the quiescent mode circuit as well as the components for operating the operating mode circuit. Both circuits are preferably provided with a common control line, which is used for applying signals to the interconnected inputs of the microprocessor and into which the external switch is inserted. These refinements result in space savings regarding the circuit design and reduce the number of required components to a minimum. In addition, only electronic components of the simplest type are required for realizing such a circuit arrangement.